Brushless direct current (DC) motors have a variety of applications within a variety of industries. For example, the aerospace industry often uses brushless DC motors for servo and remote control tasks such as controlling the aircraft control surface, and servovalve or fuel valve operation.
One conventional brushless DC motor includes a rotor, a stator and a motor controller. The rotor typically includes a shaft and a set of permanent magnets mounted to the shaft. The stator typically includes a motor casing and coils which are typically wound in slots inside of the motor casing. The rotor shaft couples to the motor casing such that the rotor is capable of rotating relative to the casing, and such that the stator coils surround the set of permanent magnets mounted to the shaft.
The motor controller typically includes Hall-effect sensors and a control circuit. The Hall-effect sensors sit adjacent to the motor coils fixed to the motor stator and in close proximity to the rotor magnets to enable the Hall-effect sensors to adequately sense a magnetic field by the permanent magnets of the rotor. The control circuit electrically connects to both the Hall-effect sensors and the stator coils.
During this magnetic field sensing operation, the Hall-effect sensors provide electric signals to the control circuit which enables the control circuit to determine the angular position of the rotor within the stator. The control circuit can consequently control the motor commutation process and output currents to the stator coils in a way that controls the position of the rotor relative to the stator. The currents in the stator coils generate a magnetic field, which produces torque by interaction with the permanent magnets on the rotor shaft pushing the rotor to rotate about the rotor shaft to a new position. Such operation enables the brushless DC motor to remotely perform tasks, e.g., to make servovalve adjustments to modify a position of a wing flap, to change a metering position of a fuel valve, etc.